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Low-temperature methane oxidation over oxide-supported Pd catalysts coated on a metal or ceramic honeycomb was investigated for gas turbine applications. Al2O3 and SnO2 were used as washcoat material, and a Fe–Cr–Al alloy and cordierite were adopted as metal and ceramic honeycombs, respectively. Pd catalysts on the honeycomb were prepared by varying washcoat loading and washcoat calcination temperature. It was found that the catalytic activities of Pd/SnO2 on metal and ceramic honeycombs improved with increasing washcoat loading and precalcination temperature of the washcoat material. Especially, significant enhancement of the catalytic activity appeared for Pd/SnO2/ceramic honeycomb as the washcoat loading increased from 150 to 200 g/l. The catalytic activity of the honeycomb catalysts was examined under high pressure and space velocity. The temperature at which the increase in CH4 conversion became noticeable was shifted to higher temperature compared to the experiments at lower space velocity and ambient pressure. CH4 conversion over the honeycomb catalysts fluctuated as the catalyst bed inlet temperature was raised. Pd/SnO2/ceramic honeycomb exhibited the highest stable activity for low-temperature methane oxidation. [Copyright &y& Elsevier]

The influence of water vapor on the activity for low-temperature methane oxidation over oxide-supported catalysts such as Pd/Al2O3, Pd/SnO2, and Pd/Al2O3-36NiO was studied. It was found that Pd/Al2O3 was deactivated most significantly due to water vapor, and that Pd/Al2O3-36NiO was most insensitive to water vapor. The catalytic activity of Pd/Al2O3 decreased monotonically as water vapor concentration increased, whereas Pd/SnO2 and Pd/Al2O3-36NiO showed almost constant activity under higher water vapor concentrations. The catalytic activity at high steam concentration was in the following order: Pd/SnO2>Pd/Al2O3-36NiO>Pd/Al2O3. Kinetic analysis with methane adsorption as the rate-limiting step was applied to evaluate the water inhibiting effect. Pd/Al2O3 displayed the most negative value of the enthalpy of water adsorption, while Pd/SnO2 and Pd/Al2O3-36NiO exhibited similar water adsorption enthalpy.Deactivation and regeneration of Pd/SnO2 and Pd/Al2O3 catalysts were investigated by cyclic feed of water vapor. Both the catalysts were deactivated rapidly upon switching on water feed, and then they regenerated gradually to the initial activity after the water feed was switched off. [Copyright &y& Elsevier]